Caching and tiering for cloud storage

ABSTRACT

Various systems and methods for caching and tiering in cloud storage are described herein. A system for managing storage allocation comprises a storage device management system to maintain an access history of a plurality of storage blocks of solid state drives (SSDs) managed by the storage device management system; and automatically configure each of a plurality of storage blocks to operate in cache mode or tier mode, wherein a ratio of storage blocks operating in cache mode and storage blocks operating in tier mode is based on the access history.

TECHNICAL FIELD

Embodiments described herein generally relate to storage devicemanagement and in particular, to caching and tiering for cloud storage.

BACKGROUND

A solid-state drive (SSD) is a data storage device that uses integratedcircuit assemblies as memory to store data persistently. SSD drives useinterfaces compatible with traditional block input/output (I/O) harddisk drives (HHD), which provides backward compatibility and simplereplacement in various applications. Most SSDs use NAND-based flashmemory, which retains data without power. SSDs have been incorporatedinto storage arrays as a cache mechanism. SSDs may also be used forstorage. Current implementations of SSDs for storage and caches involvesmanaging both independently. The SSDs may be allocated from a pool ofdevices. As such, there is a limited number of SSDs available forstorage or cache.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. Some embodiments are illustrated by way of example, and notlimitation, in the figures of the accompanying drawings in which:

FIG. 1 is a schematic drawing illustrating a computing environment forcaching and tiering in cloud storage, according to an embodiment;

FIG. 2 is a chart illustrating time-varying SSD storage poolpartitioning based on data access metrics, according to an embodiment;

FIG. 3 is a block diagram illustrating multiple storage pools, accordingto an embodiment;

FIG. 4 is a block diagram illustrating a storage pool with a flexibletiering design, according to an embodiment;

FIG. 5 is a block diagram illustrating a system for managing storageallocation, according to an embodiment;

FIG. 6 is a flowchart illustrating a method of managing storageallocation, according to an embodiment; and

FIG. 7 is a block diagram illustrating an example machine upon which anyone or more of the techniques (e.g., methodologies) discussed herein mayperform, according to an example embodiment.

DETAILED DESCRIPTION

Systems and methods described herein provide caching and tiering forcloud storage. In cloud storage, a combination of HHDs and SSDs may beused. For top tier service, SSDs may be used as the primary storagemechanism, where lower tier services provide HHDs for storage. Inaddition, SSDs may be used as caches between either SSD-based top-tierservices or HDD-based lower-tier services.

Current implementations of SSDs for storage and cache involves managingboth independently. The SSDs may be allocated from a pool of devices. Assuch, there is a limited number of SSDs available for storage or cache.Administrators typically guess at anticipated I/O patterns based on thecontents stored, user base, or other aspects, and then add in somemargin of error when allocating the SSD pool for either storage orcache. Once the allocation is committed, there is no simple way toreassign solid state capacity to either the storage or cache operations.Instead, reassignment typically involves reconfiguring the storagesubsystem, which may entail downtime, negotiation with customers, andstorage administrator resources. Consequently, the storage service ownermay size the overall SSD pool more conservatively to meet theanticipated demand for Input/Output Operations per Second (IOPS),resulting in a higher overall solution cost. Additionally, today'sstorage designs tend to share consolidated caching resources acrossseveral storage pools, resulting in I/O contention across the pools.

Storage pools usually include multiple tiers of devices. A device tierrefers to a collection of similar or same devices or device types, whichprovide approximately equivalent performance. Device tiers areconventionally organized based on the rough description of devices, suchas by disk size (e.g., 500 GB, 1 TB, and 2 TB drives organized intoseparate tiers) or by disk rotation speeds (e.g., 7.2K rpm and 10K rpmdrives organized into separate tiers) or by some combination of drivecapacity and rotation speed.

The mechanisms described herein discuss an adaptive integrated solidstate caching and tiering performed dynamically and automatically toallocate SSD capacity between cache mode and tier mode (storage mode).This may enable the storage capacity manager to optimize the overallsolid state storage pool size, resulting in reduce acquisition costs andconfiguration management overhead. Additionally, the manager mayallocate overall solid state storage capacity on a per pool basis forboth tier and cache, thereby eliminating cross-pool contention andassociated sizing complexity. Drives may also be organized into dynamictiers, such that when a drive is added to a storage pool, the drive isadded to an existing tier or added to a newly created tier based on theIOPS density of the drive. This type of management results in lowerstorage acquisition and ongoing support costs, simplified configurationmanagement, and increased performance of storage systems.

FIG. 1 is a schematic drawing illustrating a computing environment 100for caching and tiering in cloud storage, according to an embodiment.The computing environment 100 includes a number of hosts 102 and a cloudstorage system 104, which are communicatively coupled via a network 106.A host 102 may be a device such as a smartphone, cellular telephone,mobile phone, laptop computer, tablet computer, music player, wearabledevice (e.g., watch, glasses-based device, etc.), desktop, laptop,hybrid, in-wall, or other networked device.

The network 106 may include local-area networks (LAN), wide-areanetworks (WAN), wireless variant networks (e.g., wireless LAN (WLAN)such as a network conforming to an IEEE 802.11 family of standards or awireless WAN (WWAN) such as a cellular network), the Public SwitchedTelephone Network (PSTN) network, ad hoc networks, personal areanetworks (e.g., Bluetooth) or other combinations or permutations ofnetwork protocols and network types. The network 106 may include asingle local area network (LAN) or wide-area network (WAN), orcombinations of LANs or WANs, such as the Internet. The various devicesin FIG. 1 (e.g., hosts 102) may be coupled to the network 106 via one ormore wired or wireless connections.

The cloud storage system 104 includes cloud storage operating software106 that manages a random-access memory (RAM) cache 108, an SSD storagepool 110, which includes SSDs that operate as an SSD cache 112 and as anSSD tier 114, and hard disk tiers 116. The disk tiers (e.g., SSD tier114 and hard disk tiers 116) are roughly organized according to diskperformance. In many implementations, SSD tiers are at the top of thetier hierarchy with conventional magnetic disk drives occupying themiddle and lower tiers in the tier hierarchy. The middle tiers areconventionally referred to as the performance tiers and may includeSerial Attached SCSI (SAS) drives. The lower tiers are conventionallyreferred to as the capacity tiers and may include Near Line SAS (NL-SAS)or Serial ATA (SATA) drives, which are slower performers with largercapacities. SAS disks have largely replaced older SCSI disks to becomethe standard in enterprise-grade storage. Of the three types of disks(SAS, NL-SAS, and SATA), SAS are the most reliable, maintain theirperformance, and perform better than NL-SAS and SATA disks. SAS disksare tested to perform reliably in a near 100% duty cycle, whereas NL-SASand SATA disks are designed and tested to perform at much lower levelsof duty.

At the top of the tier hierarchy is the SSD tier 114, which includesdisks from the SSD storage pool 110. The SSD storage pool 110 ispartitioned into the SSD cache 112 and the SSD tier 114. The SSD cache112 size is conventionally configured manually by an administrator whomakes a rough estimate of anticipated input/output (I/O) patterns anddemands. Once sized, there is no simply way to reassign solid statecapacity. In the embodiment illustrated in FIG. 1, the cloud storageoperating software 106 may dynamically partition the solid state storagecapacity between caching and tiering functions, which providessignificantly more cost-effective storage pool configurations comparedto manual sizing.

The cloud storage operating software 106 may be configured to monitorusage of the SSD storage pool 110. Blocks being accessed on a sustainedand continuing basis with a frequency above an access consistencythreshold may be marked as tiered, in which case the primary copy ismigrated to reside in the solid state tier 114. In this way, thesetiered blocks no longer need to be periodically flushed to the muchlower hard disk-based storage tiers 116, thereby conserving therelatively scarce IOPS and bandwidth of the much slower hard disks.Conversely, blocks whose access patterns fall below an accessconsistency threshold may be marked to be in a cached mode and stored inthe SSD cache 112, with a primary copy being retained on a hard disktier 116. Cached blocks are susceptible to be flushed or overwrittenbased on standard caching algorithms in response to changing accesspatterns. These caching algorithms allow the capacity of the SSD cache112 to be serially shared among blocks with significant time varyingaccess patterns at the cost (in terms of hard disk IOPS and bandwidth)of periodically updating the copy on the hard disk tier 116.

The relative size of the SSD cache 112 and tier 114 capacities may bedynamically adjusted using machine learning algorithms based on summaryinformation regarding block access patterns. Specifically, for eachblock, an average accesses (reads and writes) per day is tracked and ameasure of variability in the access patterns is determined Blocks witha relatively high variability indicate bursty or intermittent access,which is suitable for caching. Blocks with a relatively low variabilityindicate a steady access pattern, which is more suitable for tiering.For greater temporal resolution, variability may be measured at smallerintervals, such as hourly or less. In an embodiment, to measure accesspattern variability of a block, a ratio of an average number of accessesdivided by a standard deviation in accesses may be used. In anotherembodiment, time between accesses may be used to determine accesspattern variability.

For example, in a given period (e.g., a day), the number of accesses ofa block may be sampled multiple times (e.g., every minute). The resultis then averaged over the period to provide an average number ofaccesses. A standard deviation may be calculated for the period (e.g.,over the day with 1440 samples). A relatively low standard deviation mayrepresent a relatively consistent access pattern and conversely, arelatively high standard deviation may represent a relatively volatileor bursty access pattern. The standard deviation may be scaled by theaverage and the result may be used as an access consistency metric.

As another example, in a given period of a day, the time betweenaccesses may be measured and an average time between accesses may becalculated for multiple sub-periods (e.g., every minute). A standarddeviation of the average time between accesses over the day may becalculated with respect to the 1440 samples (per minute averages).Similar to the previous example, a relatively low standard deviation mayrepresent a consistent access pattern and vice versa.

Access consistency metrics may be calculated for every data block in thecloud storage system 104. In this manner, if a data block is initiallystored in the hard disk tier 116 and then moved to the SSD cache 112when requested by a host 102, the data block access is tracked. Iflater, the data block is flushed from SSD cache 112 because it was notaccessed and the SSD cache 112 space was needed for another data block,then the previous access is stored and maintained with the data block sothat in the future, if it is again requested and moved to SSD cache 112,the later access may be correctly accounted for in the accessconsistency metric.

Based on access frequency, the blocks may be sorted in descending orderand a cutoff targeted for the SSD storage pool 110 determined. Thecutoff may account for a small multiplier of the overall SSD capacityavailable. For this subset, the dynamic partitioning between cache andtiering functions is derived with an iterative approach starting withheuristics based thresholds for the “variableness” measure. Blocks withsteady access history are designated to be tiered and the rest arecached. The access consistency threshold may be iteratively shifted upor down with the general objective of maximizing the hit rate (e.g., SSDhit rate) weighted by the total number of accesses per time period. Inthis way, blocks with a higher number of accesses are favored overblocks with lower accesses where such blocks have similar hit rates.

FIG. 2 is a chart 200 illustrating time-varying SSD storage poolpartitioning based on data access metrics, according to an embodiment.The SSD storage pool 110 may be partitioned between an SSD cache 112 andSSD tier 114. The x-axis of the chart 200 is access consistency of ablock and the y-axis of the chart 200 is average access frequency of theblock. Note that the low end of the y-axis is medium-high accessfrequency. This is due to the fact that only blocks that have at least amedium-high access frequency will be stored in SSD storage. Those blocksthat have lower access frequency are likely stored in capacity storage(e.g., hard disk tier 116). Blocks that have an access consistency thatsubstantially varies over time are stored in SSD cache 112. Blocks thatare used frequently and have a relatively consistent I/O pattern (e.g.,a high access consistency) are stored in SSD tier 114. The capacity ofSSD storage that is assigned to cache mode or tier mode is determined bythe access consistency threshold and the capacity used for either cacheor tier may vary over time.

FIG. 3 is a block diagram illustrating multiple storage pools, accordingto an embodiment. Each of Pool A 302 and Pool B 304 includes an extremeperformance tier, a performance tier, and a capacity tier. As discussedabove, the extreme performance tier typically includes SSDs, theperformance tier typically includes fast, high-performance, reliable SASdrives, and the capacity tier typically includes lower performance,high-capacity, NL-SAS drives. NL-SAS drives may be SAS drives with lowerspecifications (e.g., slower spindle speed or a lower mean time betweenfailure (MTBF)). NL-SAS drives may also be other drive types (e.g.,SATA) with an interposer or bridge to translate between SAS commands andnative drive commands (e.g., SATA commands).

In contrast to conventional SSD cache operations where the SSD cache isshared among pools, in the configuration shown in FIG. 3, each pool (302and 304) includes its own solid state storage pool to adaptively anddynamically partition into a cache and a tier. By not sharing a logicalSSD cache across pools, contention is eliminated and performance of eachpool is increased.

In conventional implementations, the pools (302 and 304) are organizedby basing the tiers on drive types (e.g., SSD, SAS, NL-SAS). In theseconventional implementations, for each tier, a single drive type may bespecified by an administrator. For example, when configuring a SAS tier,an administrator may be presented a list of drive types and capacities,such that the administrator may specify 300 GB 15K RPM SAS drives or 600GB 10K RPM drives or 900 GB 10K drives, but not a mix of these drivetypes/capacities.

The downside of these types of restrictions is that the cloud storageadministrator is forced to grow pools based on automated storage tieringwith drive types that were selected initially. To be able to use newerdrive types, the cloud storage administrator is forced to startconfiguring new pools, which may result in fragmentation of storagecapacity across a larger number of pools, each of which may have muchlower capacity than a single unified storage pool. This storage capacityfragmentation results in multiple inefficiencies that collectively drivea higher overall total cost of ownership and associated competitiveconcerns.

To overcome these limitations, storage tiers may be designed andimplemented based on drive performance metrics instead of just roughdevice classifications (e.g., SSD, SAS, NL-SAS). In an embodiment, theindividual drive capacity and drive IOPS are used together in acomposite metric referred to as IOPS Density. IOPS Density is the IOPSdivided by capacity. Tiers may be arranged in order or IOPS Density.

An example hierarchy of tiers based on IOPS Density is:

Top tier SSD (highest IOPS Density) SAS tiers 10K RPM - 300 GB 10K RPM -600 GB 10K RPM - 900 GB 10K RPM - 1.2 TB NL-SAS tiers 7.2K RPM - 2 TB7.2K RPM - 3 TB 7.2K RPM - 4 TB (lowest IOPS Density)

Data placement algorithms do not need to be changed in principle—onlyadapted to accommodate a larger number of tiers. Typically, the approachis to start by populating the highest performing tiers first—up to aspecified threshold and then migrating the least active data blocks tothe next lower performance storage tier until that fills up to itsspecified threshold and continue the ripple down effect to the lowestperformance tier. This provides the best overall performance bymaximizing the I/O traffic to the best performing tiers in the storagepool.

FIG. 4 is a block diagram illustrating a storage pool with a flexibletiering design, according to an embodiment. In contrast to the poolsillustrated in FIG. 3, the pool illustrated in FIG. 4 includes severalsub-tiers within each of the performance tier 402 and the capacity tier404. The sub-tiers are organized according to IOPS Density. Althoughonly a few sub-tiers are illustrated, it is understood that any numberof sub-tiers may be implemented. Further, although only one SSD tier isillustrated, it is understood that additional SSD tiers may beimplemented according to the same principles described above. Further,while the base tiers are illustrated (e.g., SSD, SAS, NL-SAS), it isunderstood that the tier names may be removed and that drives may beorganized by IOPS Density and that they may be used as either“performance” or “capacity” drives according to various thresholds basedon IOPS Density.

FIG. 5 is a block diagram illustrating a system 500 for managing storageallocation, according to an embodiment. The system 500 may include astorage device management system 502. The storage device managementsystem 502 may be implemented in full or in part by the cloud storageoperating software 106.

The storage device management system 502 may be configured to maintainan access history of a plurality of storage blocks of solid state drives(SSDs) managed by the storage device management system and automaticallyconfigure each of a plurality of storage blocks to operate in cache modeor tier mode, where a ratio of storage blocks operating in cache modeand storage blocks operating in tier mode is based on the accesshistory. In an embodiment, the storage device management system 502 isto recurrently perform these operations, such as daily, hourly, everyminute, etc.

In an embodiment, to maintain the access history, the storage devicemanagement system is to determine an average access frequency of each ofthe plurality of storage blocks and determine an access consistency ofeach of the plurality of storage blocks. In a further embodiment, toautomatically configure each of the plurality of storage blocks, thestorage device management system is to configure storage blocks with arelatively high average access frequency and a relatively high accessconsistency to operate in tier mode and configure storage blocks with arelatively low average access frequency and a relatively low accessconsistency to operate in cache mode.

In another embodiment, the storage device management system 502 isconfigured to sort the plurality of storage blocks based on the accessconsistency. In a further embodiment, the storage device managementsystem 502 is to identify an access consistency threshold, and toautomatically configure each of the plurality of storage blocks, thestorage device management system 502 is to configure storage blocks withan access consistency that exceeds the access consistency threshold tooperate in tier mode. In a further embodiment, to automaticallyconfigure each of the plurality of storage blocks, the storage devicemanagement system 502 is to configure storage blocks with an accessconsistency that does not exceed the access consistency threshold tooperate in cache mode.

In an embodiment, the storage device management system 502 is to adjustthe access consistency threshold to maximize a hit-rate of the pluralityof storage blocks stored on the SSDs.

In an embodiment, the storage device management system 502 is to adjustthe access consistency threshold based on a weighted function of theaccess consistency weighted by the average access frequency of each ofthe plurality of storage blocks for a time period.

In an embodiment, the access consistency of each of the plurality ofstorage blocks is a ratio of a standard deviation of accesses and theaverage access frequency of each respective block of the plurality ofstorage blocks.

In an embodiment, to determine the access consistency of the pluralityof storage blocks, the storage device management system is to use aweighted average of the access consistency of the respective block inthe plurality of blocks.

In an embodiment, the SSDs managed by the storage device managementsystem 502 are not shared across device pools. As discussed above,maintaining separate SSD caches per pool may reduce cross-poolcontention and increase performance.

In an embodiment, the storage device management system 502 manages aplurality of storage devices organized in a plurality of tiers, andwherein the storage device management system is to identify a new driveto be incorporated into the plurality of storage devices, identify adata transmission metric of the new device, and incorporate the newdrive into the plurality of tiers based on the data transmission metric.In a further embodiment, the data transmission metric comprises aninput/output operations per second (IOPS) per gigabyte. In anembodiment, the IOPS of the new device is obtained from datasheetinformation corresponding to the new device. In another embodiment, toobtain the IOPS of the new device, the storage device management systemis to monitor the new device during operation in the plurality ofstorage devices; and measure an average IOPS of the new device based onthe monitoring.

In an embodiment, to incorporate the new drive into the plurality oftiers, the storage device management system is to identify a new tierfor the new device and incorporate the new tier into the plurality oftiers.

In an embodiment, the plurality of tiers are organized based on datatransmission metrics of the plurality of storage devices from fasteroperation to slower operation. Tiers may be composed of ranges of IOPSDensities to account for minor variations in driver performance. Forexample, two SAS drives where one is a 2 GB 10K RPM drive with 145 IOPSand another is a 3 GB 15 RPM with a 220 IOPS may be placed into the sametier because the 2 GB drive has an IOPS Density of 72.5 and the 3 GBdrive has an IOPS Density of 73.3. Such a tier may be composed of drivewith IOPS Densities ranging from 72.0 to 74.0, for example.

FIG. 6 is a flowchart illustrating a method 600 of managing storageallocation, according to an embodiment. At block 602, at a storagedevice management system, an access history of a plurality of storageblocks of solid state drives (SSDs) managed by the storage devicemanagement system is maintained. In an embodiment, the method 600includes recurrently performing the automatic configuration.

In an embodiment, maintaining the access history comprises determiningan average access frequency of each of the plurality of storage blocksand determining an access consistency of each of the plurality ofstorage blocks. In a further embodiment, automatically configuring eachof the plurality of storage blocks comprises configuring storage blockswith a relatively high average access frequency and a relatively highaccess consistency to operate in tier mode and configuring storageblocks with a relatively low average access frequency and a relativelylow access consistency to operate in cache mode.

In a further embodiment, the method 600 includes sorting the pluralityof storage blocks based on the access consistency. In a furtherembodiment, the method 600 includes identifying an access consistencythreshold and where automatically configuring each of the plurality ofstorage blocks comprises configuring storage blocks with an accessconsistency that exceeds the access consistency threshold to operate intier mode.

At block 604, each of a plurality of storage blocks is automaticallyconfigured by the storage device management system, to operate in cachemode or tier mode, where a ratio of storage blocks operating in cachemode and storage blocks operating in tier mode is based on the accesshistory.

In an embodiment, automatically configuring each of the plurality ofstorage blocks comprises configuring storage blocks with an accessconsistency that does not exceed the access consistency threshold tooperate in cache mode.

In an embodiment, the method 600 includes adjusting the accessconsistency threshold to maximize a hit-rate of the plurality of storageblocks stored on the SSDs.

In an embodiment, the method 600 includes adjusting the accessconsistency threshold based on a weighted function of the accessconsistency weighted by the average access frequency of each of theplurality of storage blocks for a time period.

In an embodiment, the access consistency of each of the plurality ofstorage blocks is a ratio of a standard deviation of accesses and theaverage access frequency of each respective block of the plurality ofstorage blocks.

In an embodiment, determining the access consistency of the plurality ofstorage blocks comprises using a weighted average of the accessconsistency of the respective block in the plurality of blocks.

In an embodiment, the SSDs managed by the storage device managementsystem are not shared across device pools.

In an embodiment, the storage device management system manages aplurality of storage devices organized in a plurality of tiers, and themethod 600 includes identifying a new drive to be incorporated into theplurality of storage devices, identifying a data transmission metric ofthe new device, and incorporating the new drive into the plurality oftiers based on the data transmission metric. In a further embodiment,the data transmission metric comprises an input/output operations persecond (IOPS) per gigabyte. In an embodiment, the IOPS of the new deviceis obtained from datasheet information corresponding to the new device.In an embodiment, the IOPS of the new device is obtained by monitoringthe new device during operation in the plurality of storage devices andmeasuring an average IOPS of the new device based on the monitoring. Themonitoring may be performed as an initial testing, configuration, orinstallation procedure when a new device is introduced to a pool.

In an embodiment, incorporating the new drive into the plurality oftiers comprises identifying a new tier for the new device andincorporating the new tier into the plurality of tiers.

In an embodiment, the plurality of tiers are organized based on datatransmission metrics of the plurality of storage devices from fasteroperation to slower operation.

Embodiments may be implemented in one or a combination of hardware,firmware, and software. Embodiments may also be implemented asinstructions stored on a machine-readable storage device, which may beread and executed by at least one processor to perform the operationsdescribed herein. A machine-readable storage device may include anynon-transitory mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a machine-readable storagedevice may include read-only memory (ROM), random-access memory (RAM),magnetic disk storage media, optical storage media, flash-memorydevices, and other storage devices and media.

Examples, as described herein, may include, or may operate on, logic ora number of components, modules, or mechanisms. Modules may be hardware,software, or firmware communicatively coupled to one or more processorsin order to carry out the operations described herein. Modules may behardware modules, and as such modules may be considered tangibleentities capable of performing specified operations and may beconfigured or arranged in a certain manner. In an example, circuits maybe arranged (e.g., internally or with respect to external entities suchas other circuits) in a specified manner as a module. In an example, thewhole or part of one or more computer systems (e.g., a standalone,client or server computer system) or one or more hardware processors maybe configured by firmware or software (e.g., instructions, anapplication portion, or an application) as a module that operates toperform specified operations. In an example, the software may reside ona machine-readable medium. In an example, the software, when executed bythe underlying hardware of the module, causes the hardware to performthe specified operations. Accordingly, the term hardware module isunderstood to encompass a tangible entity, be that an entity that isphysically constructed, specifically configured (e.g., hardwired), ortemporarily (e.g., transitorily) configured (e.g., programmed) tooperate in a specified manner or to perform part or all of any operationdescribed herein. Considering examples in which modules are temporarilyconfigured, each of the modules need not be instantiated at any onemoment in time. For example, where the modules comprise ageneral-purpose hardware processor configured using software; thegeneral-purpose hardware processor may be configured as respectivedifferent modules at different times. Software may accordingly configurea hardware processor, for example, to constitute a particular module atone instance of time and to constitute a different module at a differentinstance of time. Modules may also be software or firmware modules,which operate to perform the methodologies described herein.

FIG. 7 is a block diagram illustrating a machine in the example form ofa computer system 700, within which a set or sequence of instructionsmay be executed to cause the machine to perform any one of themethodologies discussed herein, according to an example embodiment. Inalternative embodiments, the machine operates as a standalone device ormay be connected (e.g., networked) to other machines. In a networkeddeployment, the machine may operate in the capacity of either a serveror a client machine in server-client network environments, or it may actas a peer machine in peer-to-peer (or distributed) network environments.The machine may be an onboard vehicle system, set-top box, wearabledevice, personal computer (PC), a tablet PC, a hybrid tablet, a personaldigital assistant (PDA), a mobile telephone, or any machine capable ofexecuting instructions (sequential or otherwise) that specify actions tobe taken by that machine. Further, while only a single machine isillustrated, the term “machine” shall also be taken to include anycollection of machines that individually or jointly execute a set (ormultiple sets) of instructions to perform any one or more of themethodologies discussed herein. Similarly, the term “processor-basedsystem” shall be taken to include any set of one or more machines thatare controlled by or operated by a processor (e.g., a computer) toindividually or jointly execute instructions to perform any one or moreof the methodologies discussed herein.

Example computer system 700 includes at least one processor 702 (e.g., acentral processing unit (CPU), a graphics processing unit (GPU) or both,processor cores, compute nodes, etc.), a main memory 704 and a staticmemory 706, which communicate with each other via a link 708 (e.g.,bus). The computer system 700 may further include a video display unit710, an alphanumeric input device 712 (e.g., a keyboard), and a userinterface (UI) navigation device 714 (e.g., a mouse). In one embodiment,the video display unit 710, input device 712 and UI navigation device714 are incorporated into a touch screen display. The computer system700 may additionally include a storage device 716 (e.g., a drive unit),a signal generation device 718 (e.g., a speaker), a network interfacedevice 720, and one or more sensors (not shown), such as a globalpositioning system (GPS) sensor, compass, accelerometer, or othersensor.

The storage device 716 includes a machine-readable medium 722 on whichis stored one or more sets of data structures and instructions 724(e.g., software) embodying or utilized by any one or more of themethodologies or functions described herein. The instructions 724 mayalso reside, completely or at least partially, within the main memory704, static memory 706, and/or within the processor 702 during executionthereof by the computer system 700, with the main memory 704, staticmemory 706, and the processor 702 also constituting machine-readablemedia.

While the machine-readable medium 722 is illustrated in an exampleembodiment to be a single medium, the term “machine-readable medium” mayinclude a single medium or multiple media (e.g., a centralized ordistributed database, and/or associated caches and servers) that storethe one or more instructions 724. The term “machine-readable medium”shall also be taken to include any tangible medium that is capable ofstoring, encoding or carrying instructions for execution by the machineand that cause the machine to perform any one or more of themethodologies of the present disclosure or that is capable of storing,encoding or carrying data structures utilized by or associated with suchinstructions. The term “machine-readable medium” shall accordingly betaken to include, but not be limited to, solid-state memories, andoptical and magnetic media. Specific examples of machine-readable mediainclude non-volatile memory, including but not limited to, by way ofexample, semiconductor memory devices (e.g., electrically programmableread-only memory (EPROM), electrically erasable programmable read-onlymemory (EEPROM)) and flash memory devices; magnetic disks such asinternal hard disks and removable disks; magneto-optical disks; andCD-ROM and DVD-ROM disks.

The instructions 724 may further be transmitted or received over acommunications network 726 using a transmission medium via the networkinterface device 720 utilizing any one of a number of well-knowntransfer protocols (e.g., HTTP). Examples of communication networksinclude a local area network (LAN), a wide area network (WAN), theInternet, mobile telephone networks, plain old telephone (POTS)networks, and wireless data networks (e.g., Wi-Fi, 3G, and 4G LTE/LTE-Aor WiMAX networks). The term “transmission medium” shall be taken toinclude any intangible medium that is capable of storing, encoding, orcarrying instructions for execution by the machine, and includes digitalor analog communications signals or other intangible medium tofacilitate communication of such software.

ADDITIONAL NOTES & EXAMPLES

Example 1 includes subject matter for managing storage allocation (suchas a device, apparatus, or machine) comprising: a storage devicemanagement system to: maintain an access history of a plurality ofstorage blocks of solid state drives (SSDs) managed by the storagedevice management system; and automatically configure each of aplurality of storage blocks to operate in cache mode or tier mode,wherein a ratio of storage blocks operating in cache mode and storageblocks operating in tier mode is based on the access history.

In Example 2, the subject matter of Example 1 may include, wherein tomaintain the access history, the storage device management system is to:determine an average access frequency of each of the plurality ofstorage blocks; and determine an access consistency of each of theplurality of storage blocks.

In Example 3, the subject matter of any one of Examples 1 to 2 mayinclude, wherein to automatically configure each of the plurality ofstorage blocks, the storage device management system is to: configurestorage blocks with a relatively high average access frequency and arelatively high access consistency to operate in tier mode; andconfigure storage blocks with a relatively low average access frequencyand a relatively low access consistency to operate in cache mode.

In Example 4, the subject matter of any one of Examples 1 to 3 mayinclude, wherein the storage device management system is to sort theplurality of storage blocks based on the access consistency.

In Example 5, the subject matter of any one of Examples 1 to 4 mayinclude, wherein the storage device management system is to identify anaccess consistency threshold, and to automatically configure each of theplurality of storage blocks, the storage device management system is toconfigure storage blocks with an access consistency that exceeds theaccess consistency threshold to operate in tier mode.

In Example 6, the subject matter of any one of Examples 1 to 5 mayinclude, wherein to automatically configure each of the plurality ofstorage blocks, the storage device management system is to configurestorage blocks with an access consistency that does not exceed theaccess consistency threshold to operate in cache mode.

In Example 7, the subject matter of any one of Examples 1 to 6 mayinclude, wherein the storage device management system is to adjust theaccess consistency threshold to maximize a hit-rate of the plurality ofstorage blocks stored on the SSDs.

In Example 8, the subject matter of any one of Examples 1 to 7 mayinclude, wherein the storage device management system is to adjust theaccess consistency threshold based on a weighted function of the accessconsistency weighted by the average access frequency of each of theplurality of storage blocks for a time period.

In Example 9, the subject matter of any one of Examples 1 to 8 mayinclude, wherein the access consistency of each of the plurality ofstorage blocks is a ratio of a standard deviation of accesses and theaverage access frequency of each respective block of the plurality ofstorage blocks.

In Example 10, the subject matter of any one of Examples 1 to 9 mayinclude, wherein to determine the access consistency of the plurality ofstorage blocks, the storage device management system is to use aweighted average of the access consistency of the respective block inthe plurality of blocks.

In Example 11, the subject matter of any one of Examples 1 to 10 mayinclude, wherein the storage device management system is to recurrentlyperform the automatic configuring of claim 1.

In Example 12, the subject matter of any one of Examples 1 to 11 mayinclude, wherein the SSDs managed by the storage device managementsystem are not shared across device pools.

In Example 13, the subject matter of any one of Examples 1 to 12 mayinclude, wherein the storage device management system manages aplurality of storage devices organized in a plurality of tiers, andwherein the storage device management system is to: identify a new driveto be incorporated into the plurality of storage devices; identify adata transmission metric of the new device; and incorporate the newdrive into the plurality of tiers based on the data transmission metric.

In Example 14, the subject matter of any one of Examples 1 to 13 mayinclude, wherein the data transmission metric comprises an input/outputoperations per second (IOPS) per gigabyte.

In Example 15, the subject matter of any one of Examples 1 to 14 mayinclude, wherein the IOPS of the new device is obtained from datasheetinformation corresponding to the new device.

In Example 16, the subject matter of any one of Examples 1 to 15 mayinclude, wherein to obtain the IOPS of the new device, the storagedevice management system is to: monitor the new device during operationin the plurality of storage devices; and measure an average IOPS of thenew device based on the monitoring.

In Example 17, the subject matter of any one of Examples 1 to 16 mayinclude, wherein to incorporate the new drive into the plurality oftiers, the storage device management system is to: identify a new tierfor the new device; and incorporate the new tier into the plurality oftiers.

In Example 18, the subject matter of any one of Examples 1 to 17 mayinclude, wherein the plurality of tiers are organized based on datatransmission metrics of the plurality of storage devices from fasteroperation to slower operation.

Example 19 includes subject matter for managing storage allocation (suchas a method, means for performing acts, machine readable mediumincluding instructions that when performed by a machine cause themachine to performs acts, or an apparatus to perform) comprising:maintaining, at a storage device management system, an access history ofa plurality of storage blocks of solid state drives (SSDs) managed bythe storage device management system; and automatically configuring, bythe storage device management system, each of a plurality of storageblocks to operate in cache mode or tier mode, wherein a ratio of storageblocks operating in cache mode and storage blocks operating in tier modeis based on the access history.

In Example 20, the subject matter of Example 19 may include, whereinmaintaining the access history comprises: determining an average accessfrequency of each of the plurality of storage blocks; and determining anaccess consistency of each of the plurality of storage blocks.

In Example 21, the subject matter of any one of Examples 19 to 20 mayinclude, wherein automatically configuring each of the plurality ofstorage blocks comprises: configuring storage blocks with a relativelyhigh average access frequency and a relatively high access consistencyto operate in tier mode; and configuring storage blocks with arelatively low average access frequency and a relatively low accessconsistency to operate in cache mode.

In Example 22, the subject matter of any one of Examples 19 to 21 mayinclude, sorting the plurality of storage blocks based on the accessconsistency.

In Example 23, the subject matter of any one of Examples 19 to 22 mayinclude, identifying an access consistency threshold, and whereinautomatically configuring each of the plurality of storage blockscomprises configuring storage blocks with an access consistency thatexceeds the access consistency threshold to operate in tier mode.

In Example 24, the subject matter of any one of Examples 19 to 23 mayinclude, wherein automatically configuring each of the plurality ofstorage blocks comprises configuring storage blocks with an accessconsistency that does not exceed the access consistency threshold tooperate in cache mode.

In Example 25, the subject matter of any one of Examples 19 to 24 mayinclude, adjusting the access consistency threshold to maximize ahit-rate of the plurality of storage blocks stored on the SSDs.

In Example 26, the subject matter of any one of Examples 19 to 25 mayinclude, adjusting the access consistency threshold based on a weightedfunction of the access consistency weighted by the average accessfrequency of each of the plurality of storage blocks for a time period.

In Example 27, the subject matter of any one of Examples 19 to 26 mayinclude, wherein the access consistency of each of the plurality ofstorage blocks is a ratio of a standard deviation of accesses and theaverage access frequency of each respective block of the plurality ofstorage blocks.

In Example 28, the subject matter of any one of Examples 19 to 27 mayinclude, wherein determining the access consistency of the plurality ofstorage blocks comprises using a weighted average of the accessconsistency of the respective block in the plurality of blocks.

In Example 29, the subject matter of any one of Examples 19 to 28 mayinclude, recurrently performing the automatic configuring of claim 19.

In Example 30, the subject matter of any one of Examples 19 to 29 mayinclude, wherein the SSDs managed by the storage device managementsystem are not shared across device pools.

In Example 31, the subject matter of any one of Examples 19 to 30 mayinclude, wherein the storage device management system manages aplurality of storage devices organized in a plurality of tiers, andwherein the method further comprises: identifying a new drive to beincorporated into the plurality of storage devices; identifying a datatransmission metric of the new device; and incorporating the new driveinto the plurality of tiers based on the data transmission metric.

In Example 32, the subject matter of any one of Examples 19 to 31 mayinclude, wherein the data transmission metric comprises an input/outputoperations per second (IOPS) per gigabyte.

In Example 33, the subject matter of any one of Examples 19 to 32 mayinclude, wherein the IOPS of the new device is obtained from datasheetinformation corresponding to the new device.

In Example 34, the subject matter of any one of Examples 19 to 33 mayinclude, wherein the IOPS of the new device is obtained by: monitoringthe new device during operation in the plurality of storage devices; andmeasuring an average IOPS of the new device based on the monitoring.

In Example 35, the subject matter of any one of Examples 19 to 34 mayinclude, wherein incorporating the new drive into the plurality of tierscomprises: identifying a new tier for the new device; and incorporatingthe new tier into the plurality of tiers.

In Example 36, the subject matter of any one of Examples 19 to 35 mayinclude, wherein the plurality of tiers are organized based on datatransmission metrics of the plurality of storage devices from fasteroperation to slower operation.

Example 37 includes at least one machine-readable medium includinginstructions, which when executed by a machine, cause the machine toperform operations of any of the Examples 19-36.

Example 38 includes an apparatus comprising means for performing any ofthe Examples 19-36.

Example 39 includes subject matter for managing storage allocation (suchas a device, apparatus, or machine) comprising: means for maintaining,at a storage device management system, an access history of a pluralityof storage blocks of solid state drives (SSDs) managed by the storagedevice management system; and means for automatically configuring, bythe storage device management system, each of a plurality of storageblocks to operate in cache mode or tier mode, wherein a ratio of storageblocks operating in cache mode and storage blocks operating in tier modeis based on the access history.

In Example 40, the subject matter of Example 39 may include, wherein themeans for maintaining the access history comprise: means for determiningan average access frequency of each of the plurality of storage blocks;and means for determining an access consistency of each of the pluralityof storage blocks.

In Example 41, the subject matter of any one of Examples 39 to 40 mayinclude, wherein the means for automatically configuring each of theplurality of storage blocks comprise: means for configuring storageblocks with a relatively high average access frequency and a relativelyhigh access consistency to operate in tier mode; and means forconfiguring storage blocks with a relatively low average accessfrequency and a relatively low access consistency to operate in cachemode.

In Example 42, the subject matter of any one of Examples 39 to 41 mayinclude, means for sorting the plurality of storage blocks based on theaccess consistency.

In Example 43, the subject matter of any one of Examples 39 to 42 mayinclude, means for identifying an access consistency threshold, andwherein the means for automatically configuring each of the plurality ofstorage blocks comprise means for configuring storage blocks with anaccess consistency that exceeds the access consistency threshold tooperate in tier mode.

In Example 44, the subject matter of any one of Examples 39 to 43 mayinclude, wherein the means for automatically configuring each of theplurality of storage blocks comprise means for configuring storageblocks with an access consistency that does not exceed the accessconsistency threshold to operate in cache mode.

In Example 45, the subject matter of any one of Examples 39 to 44 mayinclude, means for adjusting the access consistency threshold tomaximize a hit-rate of the plurality of storage blocks stored on theSSDs.

In Example 46, the subject matter of any one of Examples 39 to 45 mayinclude, means for adjusting the access consistency threshold based on aweighted function of the access consistency weighted by the averageaccess frequency of each of the plurality of storage blocks for a timeperiod.

In Example 47, the subject matter of any one of Examples 39 to 46 mayinclude, wherein the access consistency of each of the plurality ofstorage blocks is a ratio of a standard deviation of accesses and theaverage access frequency of each respective block of the plurality ofstorage blocks.

In Example 48, the subject matter of any one of Examples 39 to 47 mayinclude, wherein the means for determining the access consistency of theplurality of storage blocks comprise means for using a weighted averageof the access consistency of the respective block in the plurality ofblocks.

In Example 49, the subject matter of any one of Examples 39 to 48 mayinclude, means for recurrently performing the automatic configuring ofclaim 39.

In Example 50, the subject matter of any one of Examples 39 to 49 mayinclude, wherein the SSDs managed by the storage device managementsystem are not shared across device pools.

In Example 51, the subject matter of any one of Examples 39 to 50 mayinclude, wherein the storage device management system manages aplurality of storage devices organized in a plurality of tiers, andwherein the apparatus further comprises: means for identifying a newdrive to be incorporated into the plurality of storage devices; meansfor identifying a data transmission metric of the new device; and meansfor incorporating the new drive into the plurality of tiers based on thedata transmission metric.

In Example 52, the subject matter of any one of Examples 39 to 51 mayinclude, wherein the data transmission metric comprises an input/outputoperations per second (IOPS) per gigabyte.

In Example 53, the subject matter of any one of Examples 39 to 52 mayinclude, wherein the IOPS of the new device is obtained from datasheetinformation corresponding to the new device.

In Example 54, the subject matter of any one of Examples 39 to 53 mayinclude, wherein the IOPS of the new device is obtained by: monitoringthe new device during operation in the plurality of storage devices; andmeasuring an average IOPS of the new device based on the monitoring.

In Example 55, the subject matter of any one of Examples 39 to 54 mayinclude, wherein the means for incorporating the new drive into theplurality of tiers comprise: means for identifying a new tier for thenew device; and means for incorporating the new tier into the pluralityof tiers.

In Example 56, the subject matter of any one of Examples 39 to 55 mayinclude, wherein the plurality of tiers are organized based on datatransmission metrics of the plurality of storage devices from fasteroperation to slower operation.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments that may bepracticed. These embodiments are also referred to herein as “examples.”Such examples may include elements in addition to those shown ordescribed. However, also contemplated are examples that include theelements shown or described. Moreover, also contemplated are examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

Publications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this document and those documents so incorporated byreference, the usage in the incorporated reference(s) are supplementaryto that of this document; for irreconcilable inconsistencies, the usagein this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to suggest a numerical order for their objects.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with others. Otherembodiments may be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is to allow thereader to quickly ascertain the nature of the technical disclosure. Itis submitted with the understanding that it will not be used tointerpret or limit the scope or meaning of the claims. Also, in theabove Detailed Description, various features may be grouped together tostreamline the disclosure. However, the claims may not set forth everyfeature disclosed herein as embodiments may feature a subset of saidfeatures. Further, embodiments may include fewer features than thosedisclosed in a particular example. Thus, the following claims are herebyincorporated into the Detailed Description, with a claim standing on itsown as a separate embodiment. The scope of the embodiments disclosedherein is to be determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled.

What is claimed is:
 1. A system for managing storage allocation, thesystem comprising: a storage device management system to: maintain anaccess history of a plurality of storage blocks of solid state drives(SSDs) managed by the storage device management system; andautomatically configure each of a plurality of storage blocks to operatein cache mode or tier mode, wherein a ratio of storage blocks operatingin cache mode and storage blocks operating in tier mode is based on theaccess history; wherein to maintain the access history, the storagedevice management system is to: determine an average access frequency ofeach of the plurality of storage blocks; and determine an accessconsistency of each of the plurality of storage blocks; and wherein toautomatically configure each of the plurality of storage blocks, thestorage device management system is to: configure storage blocks with arelatively high average access frequency and a relatively high accessconsistency to operate in tier mode; and configure storage blocks with arelatively low average access frequency and a relatively low accessconsistency to operate in cache mode.
 2. The system of claim 1, whereinthe storage device management system is to sort the plurality of storageblocks based on the access consistency.
 3. The system of claim 2,wherein the storage device management system is to identify an accessconsistency threshold, and to automatically configure each of theplurality of storage blocks, the storage device management system is toconfigure storage blocks with an access consistency that exceeds theaccess consistency threshold to operate in tier mode.
 4. The system ofclaim 3, wherein to automatically configure each of the plurality ofstorage blocks, the storage device management system is to configurestorage blocks with an access consistency that does not exceed theaccess consistency threshold to operate in cache mode.
 5. The system ofclaim 3, wherein the storage device management system is to adjust theaccess consistency threshold to maximize a hit-rate of the plurality ofstorage blocks stored on the SSDs.
 6. The system of claim 3, wherein thestorage device management system is to adjust the access consistencythreshold based on a weighted function of the access consistencyweighted by the average access frequency of each of the plurality ofstorage blocks for a time period.
 7. The system of claim 1, wherein theaccess consistency of each of the plurality of storage blocks is a ratioof a standard deviation of accesses and the average access frequency ofeach respective block of the plurality of storage blocks.
 8. The systemof claim 1, wherein to determine the access consistency of the pluralityof storage blocks, the storage device management system is to use aweighted average of the access consistency of the respective block inthe plurality of blocks.
 9. The system of claim 1, wherein the SSDsmanaged by the storage device management system are not shared acrossdevice pools.
 10. The system of claim 1, wherein the storage devicemanagement system manages a plurality of storage devices organized in aplurality of tiers, and wherein the storage device management system isto: identify a new drive to be incorporated into the plurality ofstorage devices; identify a data transmission metric of the new device;and incorporate the new drive into the plurality of tiers based on thedata transmission metric.
 11. The system of claim 10, wherein the datatransmission metric comprises an input/output operations per second(IOPS) per gigabyte.
 12. The system of claim 11, wherein the IOPS of thenew device is obtained from datasheet information corresponding to thenew device.
 13. A method of managing storage allocation, the methodcomprising: maintaining, at a storage device management system, anaccess history of a plurality of storage blocks of solid state drives(SSDs) managed by the storage device management system; andautomatically configuring, by the storage device management system, eachof a plurality of storage blocks to operate in cache mode or tier mode,wherein a ratio of storage blocks operating in cache mode and storageblocks operating in tier mode is based on the access history; whereinmaintaining the access history comprises: determining an average accessfrequency of each of the plurality of storage blocks; and determining anaccess consistency of each of the plurality of storage blocks; andwherein automatically configuring each of the plurality of storageblocks comprises: configuring storage blocks with a relatively highaverage access frequency and a relatively high access consistency tooperate in tier mode; and configuring storage blocks with a relativelylow average access frequency and a relatively low access consistency tooperate in cache mode.
 14. The method of claim 13, further comprisingsorting the plurality of storage blocks based on the access consistency.15. The method of claim 13, further comprising identifying an accessconsistency threshold, and wherein automatically configuring each of theplurality of storage blocks comprises configuring storage blocks with anaccess consistency that exceeds the access consistency threshold tooperate in tier mode.
 16. The method of claim 15, wherein automaticallyconfiguring each of the plurality of storage blocks comprisesconfiguring storage blocks with an access consistency that does notexceed the access consistency threshold to operate in cache mode. 17.The method of claim 15, further comprising: adjusting the accessconsistency threshold to maximize a hit-rate of the plurality of storageblocks stored on the SSDs.
 18. The method of claim 15, furthercomprising: adjusting the access consistency threshold based on aweighted function of the access consistency weighted by the averageaccess frequency of each of the plurality of storage blocks for a timeperiod.
 19. The method of claim 13, wherein the access consistency ofeach of the plurality of storage blocks is a ratio of a standarddeviation of accesses and the average access frequency of eachrespective block of the plurality of storage blocks.
 20. The method ofclaim 13, wherein determining the access consistency of the plurality ofstorage blocks comprises using a weighted average of the accessconsistency of the respective block in the plurality of blocks.
 21. Atleast one machine-readable medium including instructions, which whenexecuted by a machine, cause the machine to: maintain an access historyof a plurality of storage blocks of solid state drives (SSDs) managed bythe storage device management system; and automatically configure eachof a plurality of storage blocks to operate in cache mode or tier mode,wherein a ratio of storage blocks operating in cache mode and storageblocks operating in tier mode is based on the access history; whereinthe instructions to maintain the access history comprises instructionsto: determine an average access frequency of each of the plurality ofstorage blocks; and determine an access consistency of each of theplurality of storage blocks; and wherein the instructions toautomatically configure each of the plurality of storage blockscomprises instructions to: configure storage blocks with a relativelyhigh average access frequency and a relatively high access consistencyto operate in tier mode; and configure storage blocks with a relativelylow average access frequency and a relatively low access consistency tooperate in cache mode.
 22. The at least one machine-readable medium ofclaim 21, further comprising instructions to sort the plurality ofstorage blocks based on the access consistency.
 23. The at least onemachine-readable medium of claim 22, further comprising instructions toidentify an access consistency threshold, and wherein the instructionsto automatically configure each of the plurality of storage blockscomprise instructions to configure storage blocks with an accessconsistency that exceeds the access consistency threshold to operate intier mode.
 24. The at least one machine-readable medium of claim 21,wherein the access consistency of each of the plurality of storageblocks is a ratio of a standard deviation of accesses and the averageaccess frequency of each respective block of the plurality of storageblocks.
 25. The at least one machine-readable medium of claim 21,wherein the instructions to determine the access consistency of theplurality of storage blocks comprise instructions to use a weightedaverage of the access consistency of the respective block in theplurality of blocks.